Several studies suggest possible serotonergic involvement in the neurobiology of alcoholism and panic disorder. To evaluate this possibility we administered the serotonin agonist m-chlorophenyl piperazine (m-CPP) to alcoholics, alcoholics with panic disorder and controls. By observing the drug-induced behavioral effects and measuring changes in prolactin, cortisol and ACTH we hope to make inferences about post-synaptic serotonin function in these patient populations.